Investigations concern sound detection and processing by fishes. The auditory system in fishes has a number of homologues with the auditory system in other vertebrates. Consequently, understanding functional aspects of hearing in fishes provides insight into general questions of vertebrate auditory system structural and functional relationships. Experimental investigations include measurement of hearing capabilities using operant conditioning techniques to determine hearing sensitivity and other psychophysical functions. Physiological studies are directed at understanding processing in the teleost ear and the roles of more peripheral structures, such as the swimbladder and Weberian ossicles, in sound detection and processing. Ancillary investigations include TEM and SEM studies of the ultrastructure and gross morphology of the ear in order to gain better insight into the functional anatomy of the ear in fishes. Studies are being conducted comparatively in order to ascertain when there is a 'typical' teleost auditory system or whether there are multiple mechanisms of detection and processing in fishes.